> In order to ensure that the answers of the integration differ by no> more than a constant I've been differencing the expected answer from> the Axiom answer and then taking the derivative.> > One curious pattern is that your answers differ from Axiom's answers> by non-zero constants. [...]

The first sentence above correctly asserts that it is ok for antiderivatives to differ by a constant. Yet, the second sentence finds it surprising that they do differ. So what is the problem?